The latest version is in ports. You can compile webcamd with debugging.
Then there are some options listed by "webcamd -s" which you can turn on
using "webcamd -m xxx=yyy" to get more verbose debugging. You can also
try starting "usbdump -i usbusX -f Y -s 65536" where X and Y are numbers
after ugen, before plugging the device, to see which USB errors are
happening.